Abstract : No other nation relies as heavily on combat air power for its military strength or has invested as much in it as the United States. The Department of Defense (DOD) has initiated major acquisition programs estimated to cost over $300 billion to modernize its combat air power forces over the next 15 to 20 years. These forces include about 5,900 fighter and attack aircraft, including long-range bombers equipped for conventional missions and attack helicopters; specialized combat support aircraft; advanced weapons for the combat aircraft; long-range missiles; theater air defense forces; and other key air power assets. Because difficult tradeoff decisions will likely be needed among competing air power programs as the nation moves toward balancing the budget, GAO conducted detailed assessments of six key air power missions to provide information useful to the debate. This culminating report builds on and synthesizes the findings of these six reviews and other GAO reviews of air power programs. GAO'S overall objective was to assess whether the Secretary of Defense has sufficient information from adjoint perspective to help him decide whether new investments should be made, whether programmed investments should continue to be funded, and what priority should be given to competing air power programs. To gain a broad perspective on the context in which these decisions are made, GAO sought to determine (1) how U.S. air power capabilities have changed since the end of fiscal year 1991, the year the Persian Gulf War ended; (2) what potential threat adversary forces pose to U.S. air power; (3) what contribution combat air power modernization programs will make to aggregate U.S. capabilities; and (4) how joint warfighting assessments are used to support the Secretary in making air power decisions.